Light emitting element

ABSTRACT

A light emitting element includes: a box-shaped case formed by an insulation material and having a space inside; a lead frame formed by a conductive material and fixed to the case; and a light emitting chip fixed to the lead frame. On the lead frame, a rise portion is formed in a side wall of the case or along the inner surface of the side wall. The lead frame has a first lead frame fixing the light emitting chip and a second lead frame connected to the light emitting chip by the wire bonding. At least on the first lead frame, a rise portion is formed.

TECHNICAL FIELD

The present invention relates to a light emitting element that is builtby combining together a light emitting chip and a lead frame.

BACKGROUND ART

There is one type of light emitting element called a frame laser. Theframe laser is built by fixing a pair of lead frames formed out of aconductive material in a case formed out of an insulating material, witha semiconductor laser element fixed on one of the lead frames andconnected by wire bonding to the other lead frame. Japanese PatentApplication Laid-open No. H3-188692 discloses an example of a framelaser. Japanese Patent Application Laid-open No. 2003-152228 disclosesan example of a light emitting element having a light emitting diodefixed on a lead frame.

Semiconductor lasers are widely used in writing data onto opticalrecording media or reading data therefrom. Due to a recent trend towardlarge capacity optical discs, the volume of data to be read and writtenhas significantly increased, leading to demand for semiconductor laserscapable of exerting higher power.

The increase in the power exerted by a semiconductor laser results in anincrease in the volume of heat generated. The increase in thetemperature of a light emitting element causes problems such asdeformation or discoloration of the case that encloses the semiconductorlaser, requiring more effective measures against heat.

One common measure against heat is to increase the area of the leadframe so as to improve heat dissipation. Simply increasing the area ofthe lead frame, however, may result in the enlarged portion protrudingout of the case. The portion protruding out of the case requiresinsulation, leading to an increase in the number of processes, which inturn leads to higher cost. Enclosing the entire lead frame including theenlarged portion inside the case so as to omit the need for insulationleads to overall upsizing, which goes against the downsizing trend ofcomponents.

DISCLOSURE OF THE INVENTION

In view of the above-mentioned problems, it is an object of the presentinvention to enclose a light emitting chip with a lead frame with a viewto preventing deformation and discoloration of a case and with a view toimproving heat dissipation achieved by the lead frame in order to permitthe light emitting chip to exert higher power.

To achieve the above object, a light emitting element of the presentinvention is structured as follows. According to a first aspect of thepresent invention, a light emitting element includes: a box-shaped caseformed out of an insulating material and having a hollow portion inside;a lead frame formed out of a conductive material and fixed in the case;and a light emitting chip fixed on the lead frame, wherein the leadframe has a rise portion formed so as to be located inside a side wallof the case. This structure permits the heat emitted by the lightemitting chip fixed on the lead frame to dissipate through the riseportion, thereby checking an increase in the temperature of the case.This in turn avoids the deformation and discoloration of the case,thereby permitting the light emitting chip to exert higher power withoutconcern over such phenomena.

According to a second aspect of the invention, in the light emittingelement structured as described above, the rise portion is formed bybending both side edges of the lead frame. This structure permits therise portion to be formed only by adding a bending process to theforming processes of the lead frame, making it easy to fabricate.

According to a third aspect of the invention, in the light emittingelement structured as described above, the lead frame includes a firstlead frame on which the light emitting chip is fixed and a second leadframe connected to the light emitting chip by wire bonding, and the riseportion is formed at least on the first lead frame. This structure, inwhich the rise portion is formed at least on the first lead frame onwhich the light emitting chip is fixed, forces heat to dissipate throughthe first lead frame heated to a high temperature, thereby effectivelychecking an increase in the temperature of the case.

According to a fourth aspect of the invention, a light emitting elementincludes: a box-shaped case formed out of an insulating material andhaving a hollow portion inside; a lead frame formed out of a conductivematerial and fixed in the case; and a light emitting chip fixed on thelead frame, wherein the lead frame has a rise portion formed along theinner surface of a side wall of the case. This structure permits therise portion to directly face the light emitting chip, therebypermitting the heat emitted by the light emitting chip to dissipate morequickly.

According to a fifth aspect of the invention, in the light emittingelement structured as described above, the hollow portion is surroundedby four side walls of the case, and the rise portion is formed along atleast three of the side walls. This structure prevents, by means of therise portion formed along at least the three side walls, radiation ofthe heat emitted by the light emitting chip toward the three side walls,thus avoiding heat diffusion.

According to a sixth aspect of the invention, in the light emittingelement structured as described above, the rise portion is formed bybending both side edges of the lead frame and the end edge thereoforthogonal to the side edges. This structure permits the formation ofthe rise portion simply by adding a bending process to the formingprocesses of the lead frame, making it easy to fabricate.

According to a seventh aspect of the invention, in the light emittingelement structured as described above, the lead frame includes a firstlead frame on which the light emitting chip is fixed and a second leadframe connected to the light emitting chip by wire bonding, and the riseportion is formed at least on the first lead frame. This structure, inwhich the rise portion is formed at least on the first lead frame alongthe three side walls of the case, forces heat to dissipate from thefirst lead frame heated to a high temperature through the rise portionformed along the three side walls, thereby effectively checking anincrease in the temperature of the case.

According to the eighth aspect of the invention, in the light emittingelement structured as described above, the second lead frame has a riseportion formed so as to cover a side wall of the case other than theside walls covered by the rise portion of the first lead frame. Thisstructure permits the numbers of rise portions allocated to the firstand second lead frames, respectively, to be set according to factorssuch as dimensional restrictions on the lead frame and outer dimensionsof the case, thereby optimizing heat dissipation.

According to a ninth aspect of the invention, a light emitting elementincludes: a box-shaped case formed out of an insulating material andhaving a hollow portion inside; a first lead frame and a second leadframe formed out of a conductive material and fixed in the case so as toface the hollow portion; and a light emitting chip fixed on the firstlead frame, wherein the first lead frame has a rise portion formed so asto stretch over two opposite side walls of four side walls of the casesurrounding the hollow portion, wherein the second lead frame overlapsthe first lead frame with a vertical gap left therebetween, and whereinthe second lead frame is connected to the light emitting chip by wirebonding. This structure can ensure a required area for heat dissipationeven if the number of rise portions needs to be reduced for some reason,thanks to the first lead frame having a long rise portion.

According to a tenth embodiment of the invention, in the light emittingelement structured as described above, the second lead frame is arrangedabove the first lead frame. This structure permits easy wire bonding ofthe light emitting chip.

According to an eleventh embodiment of the invention, a light emittingelement includes: a case formed out of an insulating material and havinga hollow portion formed inside so as to have a cross section so taperedas to widen upward; a first lead and a second lead each having one endarranged on the bottom surface of the hollow portion and the other endprotruding out of the case; a light emitting chip fixed on the firstlead and connected to the second lead by wire bonding in the hollowportion; and a reflecting frame formed out of a metal and fixed on theinner circumferential surface of the hollow portion with a smalldistance left from the first and second leads so as not to short-circuitthe first and second leads. This structure permits the heat emitted bythe light emitting element to efficiently dissipate through the leadsand the reflecting frame.

According to a twelfth aspect of the invention, in the light emittingelement structured as described above, a plurality of light emittingchips are arranged in the hollow portion, and the first and second leadsare arranged in the same numbers as the light emitting chips. Thisstructure permits various chip arrangements.

According to a thirteenth aspect of the invention, in the light emittingelement structured as described above, a concave portion for receiving alead is formed on the outer bottom surface of the case, and portions ofthe first and second leads that protrude out of the case are bent intothe concave portion. This structure permits the leads to remain flat atthe time of molding the case, and thus suffers less from resin leakageand permits easier fabrication than when bent leads are insert-moldedinto the case.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross section of a light emitting element according to afirst embodiment of the present invention.

FIG. 2 is a perspective view of lead frames of the light emittingelement according to the first embodiment.

FIG. 3 is a perspective view showing a modified example of the leadframes of the light emitting element according to the first embodiment.

FIG. 4 is a cross section of a light emitting element according to asecond embodiment of the present invention.

FIG. 5 is a cross section of a light emitting element according to athird embodiment of the present invention.

FIG. 6 is a perspective view of lead frames of the light emittingelement according to the third embodiment;

FIG. 7 is a perspective view showing a modified example of the leadframes of the light emitting element according to the third embodiment;

FIG. 8 is a cross section of a light emitting element according to afourth embodiment of the present invention.

FIG. 9 is a cross section of a light emitting element according to afifth embodiment of the present invention.

FIG. 10 is a plan view of a lead frame used in the light emittingelement according to the fifth embodiment.

FIG. 11 is a plan view showing one step of the fabrication process ofthe light emitting element according to the fifth embodiment.

FIG. 12 is a cross section of the light emitting element according tothe fifth embodiment, taken on line A-A shown in FIG. 11.

FIG. 13 is a cross section of the light emitting element according tothe fifth embodiment, taken on line B-B shown in FIG. 11;

FIG. 14 is a plan view showing another step, later than the one shown inFIG. 11, of the fabrication process of the light emitting elementaccording to the fifth embodiment.

FIG. 15 is a cross section of the light emitting element according tothe fifth embodiment, taken on line C-C shown in FIG. 14.

FIG. 16 is a cross section of the light emitting element according tothe fifth embodiment, taken on line D-D shown in FIG. 14.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described withreference to the accompanying drawings.

FIGS. 1 and 2 show a first embodiment of the present invention. FIG. 1is a cross section of a light emitting element. FIG. 2 is a perspectiveview of lead frames used in the light emitting element of FIG. 1.

The light emitting element includes a box-shaped case 1 formed out of aninsulating material, such as epoxy resin. The case 1 has a hollowportion 6 formed inside it surrounded by the four side walls 2, 3, 4,and 5 thereof so as to be open at the top. To the case 1 are fixed afirst lead frame 7 and a second lead frame 8. The first and second leadframes 7 and 8 are formed out of a conductive material such as copper,iron, or aluminum, and are integrally molded with the case 1.

As observed in FIG. 2, the first and second lead frames 7 and 8 aremutually symmetrical in shape. Each of the lead frames has two edgesbent upward, thereby forming rise portions 9 on the first lead frame 7and rise portions 10 on the second lead frame 8. When the case 1 ismolded, the rise portions 9 and 10 are so mounted as to be locatedinside the side walls 2 and 3, whereby the first and second lead frames7 and 8 are fixed in the case 1.

The first lead frame 7 has a light emitting chip 11 fixed on a bottomportion 12 thereof. The light emitting chip 11 is connected to thesecond lead frame 8 by wire bonding 13.

The heat generated by the light emitting chip 11 is conducted to thefirst lead frame 7, which is thus heated to a higher temperature anddissipates the heat through the rise portions 9 into the space outsidethe case 1. That is, the heat that has been conducted to the first leadframe 7 is forced to dissipate into the outside space. The second leadframe 8 receives heat from the hollow portion 6 and dissipates the heatthrough the rise portions 10 into space outside the case 1. Thusachieved heat dissipation checks an increase in the temperature of thecase 1, thereby preventing the deformation and discoloration of the case1. This therefore permits the light emitting chip 11 to be made capableof exerting higher power without concern over deformation anddiscoloration of the case 1.

The rise portions 9 and 10 can easily be molded by simply adding abending process to forming processes of the first and second lead frames7 and 8.

In the structure of FIG. 2, both the first and second lead frames 7 and8 have rise portions. Alternatively, only one of the lead frames mayhave rise portions, in which case the rise portions are extended to havea greater total length with an extension portion added thereto. FIG. 3shows, as a modified example, an example of such lead frames.

In the structure of FIG. 3, the second lead frame 8 does not have riseportions. Instead, the rise portions 9 of the first lead frame 7 formextension portions 14, 14 that extend in such a way as to include therise portions 10 of the second lead frame 8 shown in FIG. 2.Specifically, the rise portions 9 have substantially the same lengths asthe side walls 2 and 3, and stretch over two opposite side walls 4 and5. Heat dissipates through the rise portions 9, each of which has comeup to have a large area, leading to higher heat dissipation efficiencyenough to compensate the amount of heat that would dissipate through thenow eliminated rise portions of the second lead frame 8.

FIG. 4 shows a second embodiment of the present invention. FIG. 4 is across section of a light emitting element.

In the second embodiment, the light emitting element includes a firstlead frame 7 and a second lead frame 8 built with the same structure asthose shown in FIGS. 2 and 3. The first and second lead frames 7 and 8,however, have rise portions 9 and 10, respectively, which are arrangednot inside but along and in close contact with the inner surfaces of theside walls 2 and 3. Thus, the rise portions 9 and 10 directly face alight emitting chip 11, thereby permitting the heat emitted by the lightemitting chip 11 to be quickly dissipated.

FIGS. 5 and 6 show a third embodiment of the present invention. FIG. 5is a cross section of a light emitting element. FIG. 6 is a perspectiveview of lead frames used in the light emitting element of FIG. 5.

In the third embodiment, a first lead frame 7 and a second lead frame 8are mutually symmetrical in shape and structured in the followingmanner. Specifically, the first lead frame 7 includes: a bottom portion12; rise portions 9 formed by bending upward the both side edges of thebottom portion 12; a rise portion 20 formed by bending upward an endedge 18 orthogonal to the side edges; and a lead portion 16 protrudingfrom the rise portion 20. The second lead frame 8 includes: a bottomportion 15; rise portions 10 formed by bending upward the both sideedges of the bottom portion 15; a rise portion 21 formed by bendingupward an end edge 19 orthogonal to the side edges; and a lead portion17 protruding from the rise portion 21.

The rise portions 9 and 20 of the first lead frame 7 are arranged alongand in close contact with the inner surfaces of side walls 2, 3, and 4.The rise portions 10 and 21 of the second lead frame 8 are arrangedalong and in close contact with the inner surfaces of the side walls 2,3, and 5. Accordingly, the side walls 2, 3, 4, and 5 have the innersurfaces thereof all covered by the rise portions.

The lead portions 16 and 17, as shown in FIG. 5, are located atrelatively the upper portions of the side walls 4 and 5, respectively,and are so laid as to run out of a case 1 through the side walls 4 and5.

The rise portions 9, 10, 20, and 21, which are formed along the innersurfaces of the four side walls 2, 3, 4, and 5 of the case 1, preventsthe heat emitted by a light emitting chip 11 from radiating in fourdirections, thereby avoiding heat diffusion.

The rise portions may be formed along three of the four side walls ofthe case 1, instead of along all these side walls as described above. Asa result, the three rise portions prevent the heat emitted by the lightemitting chip 11 from radiating in the three directions, therebyavoiding heat diffusion.

The first lead frame 7 on which the light emitting chip 11 is fixed hasthe rise portions 9, and 20 formed along the three side walls 2, 3, and4; therefore, heat is forced by at least these three side walls todissipate through the first lead frame 7 that is heated to a highertemperature, thereby effectively avoiding an increase in the temperatureof the case 1.

The rise portion portions 9, 10, 20, and 21 are easily manufacturedsimply by adding a bending process to forming processes of the first andsecond lead frames 7 and 8.

In the structure of FIG. 6, both the first and second lead frames 7 and8 respectively have the both side edges thereof bent upward so as toform the rise portions. Alternatively, only one of the lead frames mayhave rise portions formed on the both side edges thereof, in which casethe rise portions are extended to have a greater total length with anextension portion added thereto. FIG. 7 shows, as a modified example, anexample of such lead frames.

In the structure of FIG. 7, the second lead frame 8 does not have riseportions formed on the both side edges thereof, only left with a riseportion 21 formed on the end edge thereof. Instead, the rise portions 9of the first lead frame 7 form extension portions 22 and 23 that extendin such a way as to include the side portions 10 of the second leadframe 8 in FIG. 6. Specifically, the rise portions 9 have substantiallythe same lengths as the side walls 2 and 3, and stretch over twoopposite side walls 4 and 5. As a result, the side walls 2, 3, 4, and 5have the inner surfaces thereof all covered by the rise portions 9, 20,and 21.

The rise portion 21 of the second lead frame 8 covers the side wall(side wall 5) other than those (the side walls 2, 3, and 4) covered bythe rise portions 9 and 20 of the first lead frame 7. Sharing of rolesin covering the side walls 2, 3, 4, and 5 between the first lead frame 7and the second lead frame 8 as described above permits setting suitablenumbers of rise portions allocated to the first and second lead frames 7and 8, respectively, according to factors such as the dimensionalrestrictions on a lead frame and the outer dimensions of the case 1,thereby optimizing heat dissipation.

FIG. 8 shows a fourth embodiment of the present invention. FIG. 8 is across section of a light emitting element.

In the fourth embodiment, a first lead frame 7 has an extension portion24 formed on the bottom portion thereof. The extension portion 24 passesthrough a hollow portion 6 surrounded by side walls 2, 3, 4, and 5 andreaches the inner surface of the opposite side wall 5. A second leadframe 8 is fixed with the side wall 5 in such a manner as to lie abovethe first lead frame 7. A lead portion 17 of the second lead frame 8penetrates through the side wall 5. There is provided a gap W betweenthe first lead frame 7 and the second lead frame 8.

As with the first lead frame 7 of FIG. 7, the first lead frame 7 of FIG.8 has on the both side edges thereof rise portions 9 (not shown) thathave substantially the same lengths as the side walls 2 and 3 andstretch over the two opposite side walls 4 and 5.

The structure according to the fourth embodiment permits the area of thefirst lead frame 7 to be increased without enlargement of the case 1.Even if the number of rise portions needs to be reduced for some reason,the extension portion provided to the first lead frame 7 permitsincreasing a region through which heat dissipates, thereby ensuring theamount of heat dissipation. The arrangement of the second lead frame 8above the first lead frame 7 permits easy wire bonding of a lightemitting chip 11.

In any of the first to fourth embodiments, the light emitting chip 11 isfixed on the bottom portion of the first lead frame 7, and is surroundedby the first lead frame 7 only or in collaboration with the second leadframe 8.

FIGS. 9 to 16 show a fifth embodiment of the present invention. FIG. 9is a cross section of a light emitting element. FIG. 10 is a plan viewof a lead frame. FIG. 11 is a plan view showing one step of thefabrication process of the light emitting element. FIG. 12 is a crosssection, taken on line A-A shown in FIG. 1. Similarly, FIG. 13 is across section, taken on line B-B shown in FIG. 11. FIG. 14 is a planview showing another step, later than the one shown in FIG. 11, of thefabrication processes of the light emitting element. FIG. 15 is a crosssection, taken on line C-C shown in FIG. 14. Similarly, FIG. 16 is across section, taken on line D-D shown in FIG. 14.

The light emitting element of the fifth embodiment has a package 100having a case formed out of synthetic resin and combined with leadsformed out of a metal. In manufacturing the package 100, a lead frame101 as shown in FIG. 10 is first prepared. The lead frame 101 is formedby punching band-like sheet metal so as to form a lead pattern thatrecurs with a fixed pitch. The case 102 formed out of synthetic resin isinjection-molded, in this case, insert-molded, at a predeterminedposition, with the lead frame 101 not bent but kept flat. After thepackage 100 shown in FIGS. 11 to 13 is formed in the above-mentionedmanner, the package 100 is surface-bonded or wire-bonded. At the finalstage, the leads are separated, completing the light-emitting element.The leads can be separated by pressing or other methods.

Synthetic resin having a high brightness level, e.g., white syntheticresin, is used as the material for the case 102. At one corner of thecase 102, there is formed a concave portion 103 with a triangular planshape as shown in FIG. 11. The concave portion 103 is used for polarityidentification.

The number of leads finally remaining in the case 102 after theseparation is performed at the final stage is six in total. Three ofthese leads are first leads 104 a, 104 b, and 104 c, and the remainingthree leads are second leads 105 a, 105 b, and 105 c. The first leads104 a, 104 b, and 104 c line with the second leads 105 a, 105 b, and 105c, respectively. A gap is provided between the leads for insulation.

The case 102 has a hollow portion 106 having a rectangular plan shapeand a cross section so tapered as to widen upward, and thus having anoverall shape of an inverted square pyramid. The first leads 104 a, 104b, and 104 c, and the second leads 105 a, 105 b, and 105 c are eachfixed in the case 102, with one end thereof placed on the bottom surfaceof the hollow portion 106 and the other end thereof protruded out of thecase 102.

An inner flange 107 is formed under the hollow portion 106 where theoblique surfaces forming the side surfaces intersect the bottom surface.The inner flange 107 lies over the first leads 104 a, 104 b, and 104 c,and the second leads 105 a, 105 b, and 105 c, and has a smallerthickness than the leads.

A reflecting frame 108 formed out of a metal is fixed on the innercircumferential surface of the hollow portion 106 in order toefficiently cast the light emitted by the light emitting chip. As is thecase with the hollow portion 106, the reflecting frame 108 has a crosssection so tapered as to widen upward and is fixed in close contact withthe inner circumferential surface of the hollow portion 106. Thereflecting frame 108 can be fixed by, for example, providing aconcave/convex engagement portion between the reflecting frame 108 andthe case 102. The reflecting frame 108 may be fixed by using anadhesive, or fixed temporarily by some method and then fully by resinmolding to be described later. The inner flange 107 serves forpositioning the bottom end of the reflecting frame 108 and alsopreventing short-circuit between the leads caused by the reflectingframe 108.

The reflecting frame 108 may be formed out of a material that is thesame as or different from the material used for the leads. In eithercase, it is preferable that the inner surface of the reflecting frame108 be subjected to surface treatment so as to improve lightreflectivity. In addition, it is preferable that the reflecting frame108 be structured to have a thickness equal to half or more of thethickness of the lead so as to ensure heat dissipation capability.

Three light emitting chips are fixed on the package 100 with theabove-mentioned structure by surface bonding. The light emitting chips110 are fixed on the first leads 104 a, 104 b, and 104 c, respectively,and also wire-bonded to the second leads 105 a, 105 b, and 105 c,respectively, with wires 111. The light emitting chips emit threeprimary colors (RGB), respectively. Thus, the three light emitting chipsprovided in a set can achieve full color display.

FIGS. 14 to 16 show states after the surface bonding or wire bonding iscompleted. Subsequently, mold resin 112 having light permeability is fedinto the hollow portion 106 (see FIG. 9) and then hardened. Then theleads are separated, completing the light emitting element.

A concave portion 109 for receiving the leads is formed on the outerbottom surface of the case 102. The portions of the first leads 104 a,104 b, and 104 c, and the portions of the second leads 105 a, 105 b, and105 c protruding out of the case are bent into the concave portion 109so that the outer bottom surface of the case 102 and the lead bentportions are substantially flush with each other. This decreases thefootprint of the light emitting element and also permits surfacemounting.

This light emitting element can reflect on the reflecting frame 108 thelight emitted by the light emitting chip 110 and efficiently casts thelight outside. In addition, the light emitting element can effectivelymix together a plurality of emitted light of different colors. The heatgenerated by the light emitting chip 110 is dissipated outside throughthe leads. This heat is also conducted from the lead to the reflectingframe 108 since the end of the reflecting frame 108 formed out of ametal faces the lead with a short distance left therebetween, i.e., adistance equivalent to the thickness of the inner flange 107. Thiscauses heat dissipation through the reflecting frame 108, therebyproviding better overall heat dissipation efficiency.

In manufacturing the package 100, the case 102 is injection-molded tothe lead frame 101 that is flat without any bent portions. This resultsin less resin leakage and permits easier fabrication than when a bentlead is insert-molded.

In the fifth embodiment, the plan shape of the case is, but not limitedto, rectangular. The plan shape of the case may be polygonal other thanrectangular, or a circle or an oval. The number of light emitting chipsis three in this embodiment, but it may be any number, e.g. one, two,four, or more. Any other modifications may be made without departingfrom the sprit of the present invention.

INDUSTRIAL APPLICABILITY

The present invention is widely applicable to light emitting elements ofthe type in which a pair of lead frames formed out of a conductivematerial is fixed in a case formed out of an insulating material, with alight emitting chip fixed on one of such lead frames.

1. A light emitting element comprising: a box-shaped case formed out ofan insulating material and having a hollow portion inside; a lead frameformed out of a conductive material and fixed in the case; and a lightemitting chip fixed on the lead frame, wherein the lead frame has a riseportion formed so as to be located inside a side wall of the case. 2.The light emitting element according to claim 1, wherein the riseportion is formed by bending both side edges of the lead frame.
 3. Thelight emitting element according to claim 1, wherein the lead framecomprises a first lead frame on which the light emitting chip is fixedand a second lead frame connected to the light emitting chip by wirebonding, and wherein the rise portion is formed at least on the firstlead frame.
 4. A light emitting element comprising: a box-shaped caseformed out of an insulating material and having a hollow portion inside;a lead frame formed out of a conductive material and fixed in the case;and a light emitting chip fixed on the lead frame, wherein the leadframe has a rise portion formed along an inner surface of a side wall ofthe case.
 5. The light emitting element according to claim 4, whereinthe hollow portion is surrounded by four side walls, and wherein therise portion is formed along at least three of the side walls.
 6. Thelight emitting element according to claim 5, wherein the rise portion isformed by bending both side edges of the lead frame and an end edgethereof orthogonal to the side edges.
 7. The light emitting elementaccording to claim 5, wherein the lead frame comprises a first leadframe on which the light emitting chip is fixed and a second lead frameconnected to the light emitting chip by wire bonding, and wherein therise portion is formed at least on the first lead frame.
 8. The lightemitting element according to claim 7, wherein the second lead frame hasa rise portion formed so as to cover a side wall other than the sidewalls covered by the rise portion of the first lead frame.
 9. A lightemitting element comprising: a box-shaped case formed out of aninsulating material and having a hollow portion inside; a first leadframe and a second lead frame formed out of a conductive material andfixed in the case so as to face the hollow portion; and a light emittingchip fixed on the first lead frame, wherein the first lead frame has arise portion formed so as to stretch between two opposite side walls offour side walls surrounding the hollow portion, wherein the second leadframe overlaps the first lead frame with a vertical gap lefttherebetween, and wherein the second lead frame is connected to thelight emitting chip by wire bonding.
 10. The light emitting elementaccording to claim 9, wherein the second lead frame is arranged abovethe first lead frame.
 11. A light emitting element comprising: a caseformed out of an insulating material and having a hollow portion formedinside so as to have a cross section so tapered as to widen upward; afirst lead and a second lead each having one end arranged on a bottomsurface of the hollow portion and another end protruding out of thecase; a light emitting chip fixed on the first lead and connected to thesecond lead by wire bonding in the hollow portion; and a reflectingframe formed out of a metal and fixed on an inner circumferentialsurface of the hollow portion with a small distance left from the firstand second leads so as not to short-circuit the first and second leads.12. The light emitting element according to claim 11, wherein aplurality of light emitting chips are arranged in the hollow portion,and the first and second leads are arranged in same numbers as the lightemitting chips.
 13. The light emitting element according to claim 11,wherein a concave portion for receiving a lead is formed on an outerbottom surface of the case, and wherein portions of the first and secondleads that protrude out of the case are bent into the concave portion.